driver core: fix some kernel-doc warnings in dma*.c

Fix kernel-doc warnings in drivers/base/dma*.c:

Warning(drivers/base/dma-buf.c:498): No description found for parameter 'vaddr'
Warning(drivers/base/dma-coherent.c:199): No description found for parameter 'ret'

Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/base/dma-buf.c b/drivers/base/dma-buf.c
index 24e88fe..c30f3e1 100644
--- a/drivers/base/dma-buf.c
+++ b/drivers/base/dma-buf.c
@@ -493,6 +493,7 @@
 /**
  * dma_buf_vunmap - Unmap a vmap obtained by dma_buf_vmap.
  * @dmabuf:	[in]	buffer to vunmap
+ * @vaddr:	[in]	vmap to vunmap
  */
 void dma_buf_vunmap(struct dma_buf *dmabuf, void *vaddr)
 {